Heat exchanger



Jan. 13, 1959 s. c. ORR EI'AL HEAT EXCHANGER Filed Feb. 6, 1957 m X WWWW m E e N 0W m I V Z mi A M 7 Z R 1 MW 5 5 M United w States Patent2,868,513 HEAT EXCHANGlIR Stanley C. Orr and Donald E. Kropp, Elyria,Ohio, as-

signors to Pfaudler Permutit Inc.

Application February 6, 1957, Serial No. 638,516 Claims. (Cl. 257-236)This invention relates to the heat exchanger art and is particularlyconcerned with a ferrous metal heat'exchanger lined with non-ferrousmetal which is substantially unaffected by extremely corrosive fluidsand is practically unweldable to ferrous metal.

Heretofore heat exchangers have been constructed of mild steel for useWith fluidswhich are not more than mildly corrosive and stainless steeland other metals and alloys have been used in constructing heatexchangers for use with the more highly corrosive commonfluids. However,there are certain fluids which are so corrosive that they will attackeven stainless steel. Proposals have been made to construct heatexchangers entirely of metals which can resist such highly corrosivefluids but such exchangers would be prohibitively expensive. So far aswe are aware, no heat exchanger of economical construction was known orwas available prior to the present invention which would be satisfactoryfor use with these extremely corrosive fluids.

The present invention attains its object of providing an economical heatexchanger which would be suitable for use with these extremely corrosivefluids by using mild steel or stainless steel as base metal andemploying highly resistant metals such as titanium, tantalum andzirconium to make or cover the steel parts of the heat exchanger. withwhich such corrosive fluid would otherwise come into contact.

This invention will be better understood by those skilled in the artfrom the following specification and the accompanying drawings in which:i

Fig. l is a fragmentary side elevational view, partly in section, of aheat exchanger embodying the present invention;

Fig. 2 is an enlarged fragmentary sectional view of Fig. 1; and

Fig. 3 is a view similar to Fig. 2 but showing a modified form of theinvention.

The heat exchanger shown in Figs. 1 and 2 consists of the conventional,tubular, ferrous metal shell 1 which has inlet and outlet connections 2and 3 through which fluid may flow into and out of the interior of theshell. At its ends, the shell is provided with spaced, ferrous metaltube sheets 4 which are of greater outside diameter than shell 1 andwhich are secured to the shell in any suitable manner but, preferably,by welding as indicated by weld metal 5. The usual supporting brackets 6may be welded to the outside of the shell. The shell 1 and tube sheets 4define a chamber 7 for fluid which may flow there through between theinlet 2 and outlet 3. Bonnets or domes 8 attached to the tube sheetsform chambers 9 at each end of the heat exchanger. The shell and tubesheets may be made of mild or stainless steel depending to some extenton the fluid which is to pass through the chamber.

Metal covers 10 bear against the remote or outer surfaces of tube sheets4, as is better shown in Fig. 2. Tubes are expanded, as by rolling, intothe tube receiving holes in the tube sheets and extend through covare 10and tube sheets 4 and through the chamber 7 in shell 1 and serve toconduct the highly corrosive fluid from one chamber 9 to the otherchamber 9 through chamber 7 wherein it may be subjected to heating orcooling temperatures. The outer ends of these tubes 15 are secured tothe outer surfaces of the metal sheets 19 in any suitable manner but,preferably, by being electrically welded thereto, as by the tungsten arcinert gas shielded method, the weld metal being indicated at 11. Eachtube sheet is preferably provided. with two tube grooves 13 in each tubereceiving hole for mechanical strength in the assembly.

Each bonnet or dome 8 is provided with a flanged outlet tube 17 and abolt flange 18 and has a marginal outwardly extending flange 20 toengage a gasket 21 which bears on the outer surface of cover 10. A boltring 22 bears against the outer sidej of flange 20. Bolts 24 extendthrough ring 22 and tube sheets 4 and nuts 25 are on said bolts. Bydrawing up the nuts on the bolts, a fluidtight joint may be made betweenthe flange 2t), gasket 21 and cover 10. v j

.The modification shown in Fig. 3 is quite like that shown in Fig. 2,the differences being in the details of the dome. The bonnet or domeconsists of a ferrous metal outer part8a and a liner 8b of non-ferrousmetal like that of parts 10 and 15. The part So has a bolt ring 22awelded to it and provided with holes for bolts 24. The liner 8b coversthe inner surface of dome part do and has a flange 20a to project intothe space between and engage ring 22a and gasket 21. This flange isshown 1 as being attached by weld metal to the remainder of liner 8b. InFig. 3 the cover 1011 is thicker than cover 10 of Fig. 2 and the endsurfaces of tubes 15 lie within the covers'and are welded to the coversby weld metal 11 also lying between the side surfaces of the covers.

According to the present invention, all parts of the illustrated heatexchanger which are to come into contact with the extremely corrosivefluids are composed of non-ferrous metals and alloys which aresatisfactorily resistant to those fluids, and which are substantiallynonweldable to ferrous metals. Examples of such metals are titanium,tantalum and zirconium and alloys of each.

' Since thesejmetals and alloys cannot be satisfactorily welded toferrous metals the parts made of those metals are, according to thepresent invention, welded to each other and are so arranged and socooperate with the ferrous metal parts that they protect the ferrousmetal parts from contact with the corrosive fluids.

The welding of the non-ferrous parts is described above and thearrangement of those parts with the ferrous metal parts is shown in thedrawings. There the covers 10' and Mia which protect the tube sheets areclamped against those sheets by bolts 24 and ring 22 or 22a. Shell 1prevents movement of the tube sheets toward and away from each otherxandalso from covers lo and Ida. Furthermore, the tubes are rolled into thetube sheets and hence firmly fastened thereto. Thus the welds which jointhe tubes to the covers are not required to absorb large forces due todifferential expansion and contraction of dissimilar metals.

While the foregoing specification names certain nonmetals and theiralloys, it is to be understood that those metals are merely illustrativeof the class of metals which are characterized by being resistant toextremely corrosive fluids and by being substantially non-weldable toferrous metal and that the present invention contemplates the use of anyof the metals of that class.

Having thus described this invention in such full, clear, concise andexact terms as to enable any person skilled in the art, to which itpertains, to make and use the same, and having set forth the best modecontemplated of carrying out this invention, we state that thesubject-matter which we regard as being our invention is particularlypointed out and distinctly claimed in what is claimed, it beingunderstood that equivalents or modifications of, or substitutions for,parts of the above specifically described embodiment of the inventionmay be made without departing from the scope of the invention as setforth in what is claimed.

What is claimed is:

1. A heat exchanger comprising spaced, ferrous metal tube sheets, coverson the remote outer surfaces of said tube sheets, tubes extendingthrough and expanded into engagement with said tube sheets, weld metaljoining the ends of said tubes to said covers, said covers and tubesbeing composed of non-ferrous metal resistant to extremely corrosivefluids and substantially non-Weldable to ferrous metal, and means forsecuring the covers to the tube'sheets and serving to maintain thecovers in contact with the adjacent tube sheets during changes intemperature.

2. The combination of elements set forth in claim 1 in which the saidnon-ferrous metal parts are composed of metal selected from the group ofmetals consisting of titanium, tantalum, zirconium and their alloys.

3. A heat exchanger comprising a tubular, ferrous metal shell,ferrousmetal tube sheets of greater diameter than the shell andconnected to the shell at its ends to define therewith a chamber forfluid, covers on the remote outer surfaces of said tube sheets, tubesextending through said chamber and tube sheets and expanded intoengagement With said tube sheets, Weld metal joining the ends of saidtubes to said covers, bonnets for the ends of '4 said exchanger definingwith said covers chambers for extremely corrosive fluid flowing into andthrough said tubes, said covers, tubes and bonnets being composed ofnon-ferrous metal resistant to said fluids and substantially unweldableto ferrous metal, and means for securing the bonnets to the tube sheets.

4. A heat exchanger comprising a tubular, ferrous metal shell, ferrousmetal'tube sheets of greater diameter than the shell and connected tothe shell at its ends to define therewith a chamber for fluid, covers onthe remote outer surfaces of said tube sheets, tubesextending throughsaid chamber and tube sheets and rolled into said tube sheets, weldmetal joining the ends of said tubes to said covers, bonnets for theends of said exchanger defining with said covers chambers for extremelycorrosive fluid flowing into and through said tubes, each of saidbonnets including an outer part and an inner liner,

said covers, tubes and liners being composed of non ferrous metalresistant to said fluids and substantially non-Weldable to ferrousmetal, and means for securing the bonnets to the tube sheets.

5. The combination of elements set forth in claim 3 in which the saidnon-ferrous parts are composed of metal selected from the groupconsisting of titanium, tantalum, and zirconium and their alloys.

References Cited in the file of this patent UNITED STATES PATENTS2,108,087 Thayer Feb. 15,1938 2,336,879 Mekler Dec. 14, 1943 2,618,846Morris et a1. Nov. 25, 1952. 2,785,459 Carpenter Mar. 19, 1957

